Disruptors are used to disarm or to disable explosive devices. In general, the disrupter is deployed remotely from an explosive device and uses a projectile to disable the explosive device without initiating the explosive material contained in the device. One type of disruptor is a water cannon, which uses water as the projectile. In a water cannon, a charge of water is discharged from the cannon under high pressure or velocity using, for example, a propellant charge contained in the water cannon. The propellant charge, upon initiation, expands through the barrel of the water cannon, driving a plunger or similar assembly that pushes the charge of water contained in the barrel out through the end of the barrel, rupturing a membrane used to close the end of the barrel to retain the charge of water within the barrel. Water cannons produce a charge of water moving at very high velocity, high enough to disrupt an explosive device. This discharge of water, however, produces an equally forceful and violent recoil in the water cannon, necessitating a mounting structure of sufficient size and strength to compensate for this recoil. Such mounting structures eliminate the use of conventional water cannon as a tripod mounted device or small robotic platform held device.
Attempts have been made to reduce the recoil associated with water cannon. The desire to reduce recoil, however, is not limited to water cannons and can be found in other types of guns. For example, an aeroplane gun in a recoilless arrangement uses the powder gases in the gun to blow the barrel of the gun up through the top of the sleeve. The gun is expended along with the projectile at each shot. By this arrangement of having the gun and the projectile fly in opposite directions, comparatively small shock will be thrown on the framework of the aeroplane. Therefore, a single charge is used to produce substantially simultaneous and opposite forces to both launch a projectile and minimize the recoil associated with that launch. This device is widely known as the Davis gun, and the term Davis gun is often used to refer generally to any recoilless gun arrangement.
In another example, a device for firing a projectile for de-arming purposes includes a chamber in communication with the barrel. The chamber has a rear outlet through which material, in use, is ejected so as to counteract the recoil caused by firing the projectile. The material is expelled from the chamber through the outlet as a result of the explosion caused by the detonation of the charge. The chamber includes a piston interposed between the recoil absorbing material and each port. Both the material discharged rearwardly and the projectile can be water. When water is fired, the firing of the device ejects a single pulse of water followed by the projectile. The gas that expels the counteracting material is initially directed forwarded and has to be re-routed rearwardly to the chamber to expel the material. Therefore, an arrangement of passages to redirect the gas is required. Moreover, a portion of the force of the gas will be lost as its direction is reversed.
Similarly, another de-armer uses a single charge to move plugs to discharge water simultaneously in different directions. The igniter is formed integral with the rear discharge system which is axially disposed around the igniter. The force from the explosion moves forward initially and is then directed to the rear through one or more ports. The arrangements of these water cannons provide for water charges that are arranged as annular rings around the main barrel or the igniter. The gas from the propellant charge moves through or toward the main barrel initially, and a portion of the expanding gases are redirected through channels to a rearward direction.